Experiment: Dissection of Scoliodon (Dogfish) for External and Internal Anatomy

Aim: To perform a dissection of a Scoliodon (dogfish) specimen to observe and identify its external and internal anatomical structures.

Materials:

1. Preserved Scoliodon (dogfish) specimen

2. Dissection tray

3. Dissection kit (scalpel, dissecting scissors, forceps)

4. Gloves and safety goggles

5. Hand lens or magnifying glass

6. Ruler or calipers

7. Paper towels

8. Specimen pins

9. Anatomy reference materials (books, charts)

Experimental Procedure:

1. Place the preserved Scoliodon specimen on a dissection tray and rinse it with water to remove any excess preservative fluid.

2. Examine the external anatomy of the specimen using a hand lens or magnifying glass. Observe and identify key features such as the body shape, fins, mouth, eyes, nostrils, and skin characteristics.

3. Use a scalpel and dissecting scissors to make a longitudinal incision along the ventral side of the specimen, from the head to the tail, taking care not to damage internal organs.

4. Carefully lift and pin back the flaps of the body wall to expose the internal organs.

5. Observe and identify internal anatomical structures, including the digestive system (mouth, pharynx, esophagus, stomach, intestine), respiratory system (gills), circulatory system (heart), reproductive organs, liver, pancreas, and spleen.

6. Take measurements of selected structures using a ruler or calipers, noting their sizes and proportions.

7. Make sketches or diagrams of the external and internal anatomy of the Scoliodon specimen, labeling key structures and indicating their relative positions.

8. Clean up the dissection area, dispose of biological waste properly, and wash hands thoroughly after handling the specimen.

Observations:

1. External Anatomy:

   – Streamlined body shape with dermal denticles.

   – Dorsal, ventral, and lateral fins for propulsion and stability.

   – Ventral mouth with sharp teeth, dorsolateral eyes, and dorsal nostrils.

2. Internal Anatomy:

   – Digestive system with stomach containing prey items.

   – Respiratory gills supported by arches and filaments.

   – Two-chambered heart for circulation, reproductive organs, liver, pancreas, and spleen.

Results and Analysis:

– External features reflect marine predatory adaptation.

– Internal structures reveal complex physiology and evolutionary adaptations.

– Insights into physiology, behavior, and ecological role of Scoliodon.

– Comparative analysis aids understanding of vertebrate diversity and evolution.

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